Abstract:

In the 1960s, research on reproductive isolation in honeybees started with the pioneering work on
Apis cerana and A. mellifera of F. Ruttner. Since then, the number of recognised Apis
species increased from four to nine, and data on reproductive isolation played a key role in this
development. In this paper, we discuss the behavioural mating barriers (mating season, mating place,
sexual signals, daily mating periods), copulatory barriers (size, genitalia, mating sign) and
physiological barriers (sperm transfer, sperm storage) and postzygotic barriers (fertilisation,
development, hybrids). Allopatric A. mellifera and allopatric populations of the other species had
a uniform mating period during the afternoon hours. Sympatric honeybee species were separated mainly by
different daily mating periods. The mating period differed between populations of the same species from
different regions. The sequence of the mating periods, however, described from Sri Lanka, Thailand and
Sabah (Borneo) followed the same pattern and showed a taxonomic and size correlation: the dwarf bees (A. andreniformis and/or Apis florea) occupied the first position shortly after noon. The next
mating period was occupied by cavity-dwelling bees and at sunset, A. dorsata drones flew out for
mating. In addition, in the honeybee species that have been studied, various non behavioural mating
barriers have been demonstrated.

Correspondence and reprints: Nikolaus Koeniger
E-mail: nikolaus.koeniger@em.uni-frankfurt.de
This work is dedicated to the memory of the late Friedl Ruttner, whose unfailing enthusiasm for research
on honeybee reproduction has been an inspiration to us.